1. Field of the Invention
The present invention relates to a wireless teaching pendant for operating a control apparatus of a robot or a machine tool by wireless communication, the control apparatus of the robot or the machine tool to be operated from the wireless teaching pendant by wireless communication, and an automatic machine system including the same.
2. Description of the Related Art
In order to operate automatic machines, such as robots or computerized numerical control (CNC) machine tools (hereinbelow, simply referred to as “machine tools”), portable wireless teaching pendants are used by being connected to control apparatuses of the robots or the machine tools via wireless communication. FIG. 9 is a schematic drawing of a general automatic machine system including a control apparatus of a robot and a wireless teaching pendant. A robot 103 is illustrated as an example of an automatic machine. A control apparatus 102 for controlling the robot 103 and a portable wireless teaching pendant 101 are connected to each other by wireless communication. An operator can perform registration, edition, condition setting, and status display of an operation program regarding the robot 103 and teaching to the robot 103 using the wireless teaching pendant 101. The robot 103 can be stopped in emergency by operating the wireless teaching pendant 101.
Generally, in the automatic machine system including the control apparatus of the robot or the machine tool and the wireless teaching pendant, a LIVE signal for confirming establishment of wireless communication between the wireless teaching pendant and the control apparatus is periodically transmitted from the wireless teaching pendant to the control apparatus so as to avoid unexpected operations of the robot or the machine tool and ensure safety of surrounding machines and operators. The control apparatus cannot easily control the robot or the machine tool unless receiving the LIVE signal. FIG. 10A and FIG. 10B illustrate transmission and reception of LIVE signals in the automatic machine system including the control apparatus of the robot or the machine tool and the wireless teaching pendant. As illustrated in FIG. 10A, data for one period transmitted from the wireless teaching pendant to the control apparatus of the robot or the machine tool is constituted of a LIVE signal L and data C in which an operation content of the robot or the machine tool is specified. The wireless teaching pendant periodically transmits the LIVE signal L to the control apparatus in a constant period T, and as long as the LIVE signal L is received, the control apparatus can control the robot or the machine tool according to the operation content specified in the data C. When wireless communication becomes unstable because of some obstacles, interference with other wireless communication, and the like, and the control apparatus cannot easily receive the LIVE signal L periodically transmitted from the wireless teaching pendant as illustrated in FIG. 10B (indicated by a reference numeral F in the drawing), the control apparatus performs control of an emergency stop on the robot or the machine tool or control of a protective stop as needed.
Further, in the automatic machine system including the control apparatus of the robot or the machine tool and the wireless teaching pendant, an emergency stop and a protective stop of the robot or the machine tool are generally performed by an operation of an operator him/herself so as to ensure safety of the robot or the machine tool, the surrounding machines, and the operator in the emergency situations. In such a case, when an emergency stop switch disposed to the wireless teaching pendant is pressed by the operator, a state signal (an emergency stop signal) indicating that the robot or the machine tool is stopped in emergency is transmitted from the wireless teaching pendant to the control apparatus in a constant period, and the control apparatus received the state signal indicating performing of the emergency stop performs control to stop the robot or the machine tool in emergency.
For example, as described in Japanese Unexamined Patent Publication No. 2007-233817, there is a technique for monitoring a detection interval of a LIVE signal transmitted from the wireless teaching pendant to a controller, recognizing deterioration of a communication state of the wireless communication, and ensuring safety by stopping the machine.
In the automatic machine system including the control apparatus of the robot or the machine tool and the wireless teaching pendant, as a repeating period of the LIVE signal periodically transmitting from the wireless teaching pendant to the control apparatus of the robot or the machine tool is shorter, safety is more increased since the robot or the machine tool can be stopped in emergency in a brief disruption of wireless communication, however, a possibility becomes higher that the control apparatus cannot easily receive the LIVE signal because wireless communication becomes unstable because of obstacles, interference with other wireless communication, and the like. In other words, the shorter the repeating period of the LIVE signal is, the higher the possibility of frequently causing an emergency stop resulting from instability of wireless communication becomes, which impairs convenience.
In addition, if there is an occasion when the communication becomes unstable between the wireless teaching pendant and the control apparatus, and the control apparatus cannot easily receive the state signal (the emergency stop signal) indicating performing of the emergency stop transmitted from the wireless teaching pendant, it is dangerous since a time length and an operation distance until the robot or the machine tool stops in emergency become longer. FIG. 11A and FIG. 11B illustrate transmission and reception of emergency stop signals in the automatic machine system including the control apparatus of the robot or the machine tool and the wireless teaching pendant. When the emergency stop switch disposed to the wireless teaching pendant is pressed by the operator, a state signal indicating performing of the emergency stop as illustrated in FIG. 11A is transmitted from the wireless teaching pendant to the control apparatus at every constant period. The control apparatus received the state signal indicating performing of the emergency stop performs control to stop the robot or the machine tool in emergency. However, if there is an occasion when the wireless communication becomes unstable because of obstacles, interference with other wireless communication, and the like, and the control apparatus cannot easily receive the emergency stop signal as illustrated in FIG. 11B (indicated by the reference numeral F in the drawing), it is impossible for the control apparatus to perform control to stop the robot or the machine tool in emergency during a time period S in the drawing, and accordingly, it is dangerous since a time length and an operation distance until the robot or the machine tool stops in emergency become longer.